Domain wall motion type magnetic recording element

ABSTRACT

A magnetic domain wall movement type magnetic recording element includes: a first ferromagnetic layer which includes a ferromagnetic body; a non-magnetic layer which faces the first ferromagnetic layer; and a magnetic recording layer which faces a surface of the non-magnetic layer on a side opposite to the first ferromagnetic layer and extends in a first direction. The magnetic recording layer has a concave-convex structure on a second surface opposite to a first surface which faces the non-magnetic layer.

TECHNICAL FIELD

The present invention relates to a magnetic domain wall movement typemagnetic recording element. Priority is claimed on Japanese PatentApplication No. 2018-002469, filed Jan. 11, 2018, the content of whichis incorporated herein by reference.

BACKGROUND ART

As a next-generation non-volatile memory which replaces a flash memoryor the like of which miniaturization has come to a limit, attention hasbeen focused on a resistance change type magnetic recording device whichstores data using a resistance change type element. Examples of themagnetic recording device include a magnetoresistive random accessmemory (MRAM), a resistance random access memory (ReRAM), a phase changerandom access memory (PCRAM), and the like.

As a method of increasing a density (enlarging a capacity) of a memory,there is a method of multi-valuing recording bits per elementconstituting the memory, in addition to a method of reducing a size ofthe element itself constituting the memory.

Patent Literature 1 describes a magnetic domain wall movement typemagnetic recording element which can record multi-valued data by movinga magnetic domain wall in a magnetic recording layer. Patent Literature1 describes that multi-valued data recording is stabilized by providinga trap site in a magnetic recording layer.

CITATION LIST Patent Literature

-   [Patent Literature 1] Japanese Patent No. 5441005

SUMMARY OF INVENTION Technical Problem

The magnetic domain wall movement type magnetic recording elementdescribed in Patent Literature 1 has concavity and convexity on a sidesurface of the magnetic recording layer. The concavity and convexityserve as a trap site of the magnetic domain wall and control a positionof the magnetic domain wall. However, in order to form the concavity andconvexity on the side surface, it is necessary to performpost-processing after layers are laminated. In the case of thepost-processing, damage or the like occurs on a lamination surface onwhich a ferromagnetic layer is laminated. The magnetic domain wallmovement type magnetic recording element reads and writes data using achange in magnetoresistance. The change in magnetoresistance is causedby a change in the magnetization state between the magnetic recordinglayer and the ferromagnetic layer which sandwich a non-magnetic layer.Damage to the lamination surface causes a decrease in amagnetoresistance change rate (MR ratio). Further, Patent Literature 1also describes that the trap site is provided on the lamination surfaceof the magnetic recording layer. Also in this case, the trap sitereduces magnetization stability of a ferromagnetic body and causesnoise.

The present invention has been made in view of the above circumstances,and an object thereof is to provide a magnetic domain wall movement typemagnetic recording element which controls movement of a magnetic domainwall, curbs a decrease in a magnetoresistance change rate (MR ratio),and has little noise.

Solution to Problem

The present invention provides the following means to solve the aboveproblems.

(1) A magnetic domain wall movement type magnetic recording elementaccording to a first aspect includes a first ferromagnetic layer whichincludes a ferromagnetic body, a non-magnetic layer which faces thefirst ferromagnetic layer, and a magnetic recording layer which faces asurface of the non-magnetic layer on a side opposite to the firstferromagnetic layer and extends in a first direction, wherein themagnetic recording layer has a concave-convex structure on a secondsurface opposite to a first surface which faces the non-magnetic layer.

(2) In the magnetic domain wall movement type magnetic recording elementaccording to the above-described aspect, the first surface may have asmaller arithmetic average roughness than an arithmetic averageroughness of the second surface.

(3) In the magnetic domain wall movement type magnetic recording elementaccording to the above-described aspect, in the concave-convexstructure, an arrangement of convex portions constituting theconcave-convex structure may be irregularly spaced in plan view in alamination direction.

(4) The magnetic domain wall movement type magnetic recording elementaccording to the above-described aspect may further include a base bodywhich faces the second surface of the magnetic recording layer, and anintermediate body which is located between the base body and themagnetic recording layer.

(5) In the magnetic domain wall movement type magnetic recording elementaccording to the above-described aspect, the intermediate body may be anon-magnetic trap-reinforcing member, and the trap-reinforcing membermay be layers which are scattered on one surface of the base body or alayer which has concavity and convexity on the second surface side ofthe magnetic recording layer.

(6) In the magnetic domain wall movement type magnetic recording elementaccording to the above-described aspect, the intermediate body may havea trap-reinforcing member, and an insulating layer which covers thetrap-reinforcing member from a position near the base body, and thetrap-reinforcing member may be layers which are scattered on one surfaceof the base body or a layer which has concavity and convexity on thesecond surface side of the magnetic recording layer.

(7) In the magnetic domain wall movement type magnetic recording elementaccording to the above-described aspect, one end of the trap-reinforcingmember may be in contact with the base body, and when a surface energyof a material constituting a surface of the base body is γ_(A), and asurface energy of a material of the trap-reinforcing member is γ_(B),γ_(B)<γ_(A), and a surface energy mismatch Γ_(AB) defined by thefollowing Equation (1) may be larger than 0.5.

$\begin{matrix}{\left\lbrack {{Math}\mspace{14mu} 1} \right\rbrack \mspace{661mu}} & \; \\{\Gamma_{AB} = {2{\frac{\gamma_{A} - \gamma_{B}}{\gamma_{A} + \gamma_{B}}}}} & (1)\end{matrix}$

(8) In the magnetic domain wall movement type magnetic recording elementaccording to the above-described aspect, a plurality of recording partswhich includes the first ferromagnetic layer, the nonmagnetic layer andthe magnetic recording layer may be provided, the plurality of recordingparts may be arranged in a second direction which intersects the firstdirection, and the trap-reinforcing member may spread in a same planeover the plurality of recording parts.

(9) In the magnetic domain wall movement type magnetic recording elementaccording to the above-described aspect, a plurality of recording partswhich includes the first ferromagnetic layer, the nonmagnetic layer andthe magnetic recording layer may be provided, and the trap-reinforcingmember or a convex portion of the trap-reinforcing member may extend ina second direction which intersects the first direction over theplurality of recording parts.

(10) In the magnetic domain wall movement type magnetic recordingelement according to the above-described aspect, the concave-convexstructure may have periodicity in the first direction.

(11) In the magnetic domain wall movement type magnetic recordingelement according to the above-described aspect, the concave-convexstructure may have a concave portion or a convex portion having a firstshape, and a concave portion or a convex portion having a second shapehaving a larger volume than that of the first shape.

(12) In the magnetic domain wall movement type magnetic recordingelement according to the above-described aspect, the concave portion orthe convex portion having the second shape may be located at a positionat which the concave portion or the convex portion having the secondshape overlaps an end surface of the first ferromagnetic layer in planview in the lamination direction.

(13) In the magnetic domain wall movement type magnetic recordingelement according to the above-described aspect, the concave or convexportion having the second shape may be larger than the concave or convexportion having the first shape in the first direction.

(14) In the magnetic domain wall movement type magnetic recordingelement according to the above-described aspect, the concave or convexportion having the second shape may be larger than the concave or convexportion having the first shape in the lamination direction.

(15) In the magnetic domain wall movement type magnetic recordingelement according to the above-described aspect, a second ferromagneticlayer which reflects a magnetization state of the magnetic recordinglayer may be provided between the magnetic recording layer and thenon-magnetic layer.

(16) A magnetic domain wall movement type magnetic recording elementaccording to a second aspect includes a recording part which includes afirst ferromagnetic layer which includes a ferromagnetic body, amagnetic recording layer which is laminated on one side of the firstferromagnetic layer, extends in a first direction which intersects alamination direction, has a magnetic domain wall, and has aconcave-convex structure which traps the magnetic domain wall on a sideopposite to the first ferromagnetic layer, and a non-magnetic layersandwiched between the first ferromagnetic layer and the magneticrecording layer, and a control part which has a planarization layerlaminated on a side of the magnetic recording layer opposite to thefirst ferromagnetic layer and planarizes the concave-convex structure ofthe magnetic recording layer.

Advantageous Effects of Invention

According to the magnetic domain wall movement type magnetic recordingelement of the above-described aspect, it is possible to controlmovement of a magnetic domain wall, to curb a decrease in amagnetoresistance change rate (MR ratio) and to have little noise.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view schematically showing a magnetic domainwall movement type magnetic recording element according to a firstembodiment.

FIG. 2 is an xz sectional view schematically showing a modified exampleof the magnetic domain wall movement type magnetic recording elementaccording to the first embodiment.

FIG. 3 is a yz sectional view schematically showing a modified exampleof the magnetic domain wall movement type magnetic recording elementaccording to the first embodiment.

FIG. 4 is an xz sectional view schematically showing a modified exampleof the magnetic domain wall movement type magnetic recording elementaccording to the first embodiment.

FIG. 5 is a plan view schematically showing the magnetic domain wallmovement type magnetic recording element according to the firstembodiment.

FIG. 6A is an explanatory diagram of one example of a method formanufacturing the magnetic domain wall movement type magnetic recordingelement according to the first embodiment.

FIG. 6B is an explanatory diagram of one example of the method formanufacturing the magnetic domain wall movement type magnetic recordingelement according to the first embodiment.

FIG. 6C is an explanatory diagram of one example of the method formanufacturing the magnetic domain wall movement type magnetic recordingelement according to the first embodiment.

FIG. 6D is an explanatory diagram of one example of the method formanufacturing the magnetic domain wall movement type magnetic recordingelement according to the first embodiment.

FIG. 6E is an explanatory diagram of one example of the method formanufacturing the magnetic domain wall movement type magnetic recordingelement according to the first embodiment.

FIG. 6F is an explanatory diagram of one example of the method formanufacturing the magnetic domain wall movement type magnetic recordingelement according to the first embodiment.

FIG. 7 is a cross-sectional view schematically showing a modifiedexample of the magnetic domain wall movement type magnetic recordingelement according to the first embodiment.

FIG. 8 is a cross-sectional view schematically showing a magnetic domainwall movement type magnetic recording element according to a secondembodiment.

FIG. 9A is an explanatory diagram of one example of a method formanufacturing the magnetic domain wall movement type magnetic recordingelement according to the second embodiment.

FIG. 9B is an explanatory diagram of one example of the method formanufacturing the magnetic domain wall movement type magnetic recordingelement according to the second embodiment.

FIG. 9C is an explanatory diagram of one example of the method formanufacturing the magnetic domain wall movement type magnetic recordingelement according to the second embodiment.

FIG. 9D is an explanatory diagram of one example of the method formanufacturing the magnetic domain wall movement type magnetic recordingelement according to the second embodiment.

FIG. 9E is an explanatory diagram of one example of the method formanufacturing the magnetic domain wall movement type magnetic recordingelement according to the second embodiment.

FIG. 9F is an explanatory diagram of one example of the method formanufacturing the magnetic domain wall movement type magnetic recordingelement according to the second embodiment.

FIG. 9G is an explanatory diagram of one example of the method formanufacturing the magnetic domain wall movement type magnetic recordingelement according to the second embodiment.

FIG. 10 is a cross-sectional view schematically showing a modifiedexample of the magnetic domain wall movement type magnetic recordingelement according to the second embodiment.

FIG. 11 is a cross-sectional view schematically showing a magneticdomain wall movement type magnetic recording element according to athird embodiment.

FIG. 12 is a cross-sectional view schematically showing the magneticdomain wall movement type magnetic recording element according to thethird embodiment.

FIG. 13 is a cross-sectional view schematically showing a magneticdomain wall movement type magnetic recording element according to afourth embodiment.

FIG. 14 is a plan view schematically showing a magnetic domain wallmovement type magnetic recording element according to a fifthembodiment.

FIG. 15 is a plan view schematically showing a modified example of themagnetic domain wall movement type magnetic recording element accordingto the fifth embodiment.

FIG. 16 is a schematic diagram of a magnetic recording array accordingto a sixth embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments will be described in detail with reference tothe drawings as appropriate. In the drawings used in the followingdescription, in order to make the characteristics of this invention easyto understand, parts which become features may be enlarged forconvenience, and dimensional ratios and the like of the respectivecomponents may be different from actual ones. The materials, dimensions,and the like exemplified in the following description are merelyexamples, and the present invention is not limited thereto and can beimplemented with appropriate modifications within a range in whicheffects of the present invention are exhibited.

(Magnetic Domain Wall Movement Type Magnetic Recording Element) FirstEmbodiment

FIG. 1 is a cross-sectional view schematically showing a magnetic domainwall movement type magnetic recording element 100 according to a firstembodiment. The magnetic domain wall movement type magnetic recordingelement 100 includes a recording part 60 and a control part 75. Therecording part 60 includes a first ferromagnetic layer 10, a magneticrecording layer 20, and a non-magnetic layer 30. The recording part 60is a part for writing and reading data. The control part 75 has a basebody 80 and an intermediate body (a planarization layer) 70. The controlpart 75 is a part provided for forming a concave-convex structure whichcontrols movement of a magnetic domain wall 21 of the recording part 60.The control part 75 indirectly controls the magnetic domain wall 21 ofthe recording part 60, but the control part 75 does not actively controlthe movement of the magnetic domain wall 21. The magnetic domain wallmovement type magnetic recording element 100 shown in FIG. 1 includes afirst electrode 41 and a second electrode 42 at positions which sandwichthe first ferromagnetic layer 10 when seen in a lamination direction ofthe first ferromagnetic layer 10.

Hereinafter, a first direction in which the magnetic recording layer 20extends is defined as an x direction, a second direction orthogonal tothe x direction in a plane in which the magnetic recording layer 20extends is defined as a y direction, and a third direction orthogonal tothe x direction and the y direction is defined as a z direction. Thelamination direction of the magnetic domain wall movement type magneticrecording element 100 shown in FIG. 1 coincides with the z direction.Further, in the specification, the expression “extending in the xdirection” means, for example, that a dimension in the x direction islarger than a minimum dimension among dimensions in the x, y, and zdirections. The same applies to the case of extending in otherdirections.

“Recording Part” <First Ferromagnetic Layer>

The first ferromagnetic layer 10 includes a ferromagnetic body. Forexample, the first ferromagnetic layer 10 includes a plurality oflayers. Examples of a ferromagnetic material constituting the firstferromagnetic layer 10 include a metal selected from the groupconsisting of Cr, Mn, Co, Fe and Ni, an alloy containing at least one ofthese metals, an alloy containing these metals and at least one elementof B, C, and N, and the like. Specifically, Co—Fe, Co—Fe—B, Ni—Fe,CoHo₂, SmFe₁₂ and the like can be used.

The material forming the first ferromagnetic layer 10 may be a Heusleralloy. The Heusler alloy is a half-metal and has a high spinpolarization. The Heusler alloy is an intermetallic compound having achemical composition of XYZ or X₂YZ, X is a Co—, Fe—, Ni—, or Cu-grouptransition metal element on the periodic table or a noble metal element,Y is a Mn—, V—, Cr— or Ti-group transition metal or an elementrepresented by X, and Z is a typical element of group III to group V.Examples of the Heusler alloy include Co₂FeSi, Co₂FeGe, Co₂FeGa,Co₂MnSi, Co₂Mn₁-aFe_(a)Al_(b)Si_(1-b), and Co₂FeGe_(1-x)Ga_(c), and thelike.

The first ferromagnetic layer 10 may be an in-plane magnetization filmhaving an easy magnetization axis in an in-xy plane direction or may bea perpendicular magnetization film having an easy magnetization axis inthe z direction. In FIG. 1, the first ferromagnetic layer 10 is assumedto be an in-plane magnetization film.

When the easy magnetization axis of the first ferromagnetic layer 10 isset in the z direction (a perpendicular magnetization film), a thicknessof the first ferromagnetic layer 10 is preferably 1.0 nm or more and 2.5nm or less and more preferably 1.0 nm or more and 2.0 nm or less. Whenthe first ferromagnetic layer 10 is formed to be thin, the firstferromagnetic layer 10 has perpendicular magnetic anisotropy (interfaceperpendicular magnetic anisotropy) due to an influence of an interfacebetween the first ferromagnetic layer 10 and another layer (thenon-magnetic layer 30).

<Magnetic Recording Layer>

The magnetic recording layer 20 faces the first ferromagnetic layer 10.Here, the term “facing” means opposing another layer and includes a casein which another layer is interposed therebetween. The magneticrecording layer 20 sandwiches the first ferromagnetic layer 10 and thenon-magnetic layer 30. The magnetic recording layer 20 is laminated onone side (the lower side in FIG. 1) of the first ferromagnetic layer 10.The magnetic recording layer 20 extends in a first direction (the xdirection in FIG. 1) which intersects a lamination direction L. Themagnetic recording layer 20 has, for example, a rectangular shape whichhas a major axis in the x direction and a minor axis in the y directionin plan view in the z direction.

The magnetic recording layer 20 has a first surface 20A which faces thenon-magnetic layer 30, and a second surface 20B which is opposite to thefirst surface 20A. The magnetic recording layer 20 has a concave-convexstructure 24 which traps the magnetic domain wall 21 on the secondsurface 20B. The first surface 20A has a smaller arithmetic averageroughness (Ra) or arithmetic surface roughness than the second surface20B and is flat. The arithmetic average roughness (Ra) is a valueobtained by extracting a reference length in a direction of an averageline from a roughness curve obtained by measuring the first surface 20Aor the second surface 20B and summing and averaging absolute values ofdeviations from the average line of the extracted portion to the measurecurve. The roughness curves of the first surface 20A and the secondsurface 20B are measured along the x direction. The average line is anaverage position of a height in the z direction and extends in the xdirection. The arithmetic surface roughness is a parameter obtained byextending the arithmetic average roughness (Ra) in a surface directionand is an average of absolute values of height differences of respectivepoints with respect to an average surface of the surface. A magneticpotential energy at a convex portion 24 a is lower than that at aconcave portion 24 b. The magnetic domain wall 21 is easily trapped bythe convex portion 24 a.

The convex portions 24 a and the concave portions 24 b are periodically(equally spaced) or irregularly disposed in the x direction when seen inthe z direction. When the convex portions 24 a and the concave portions24 b are periodically disposed in the x direction (refer to FIG. 1), themagnetic domain walls 21 are trapped at predetermined intervals. As aresult, the magnetic domain wall movement type magnetic recordingelement 100 can easily perform multi-valued data recording.

FIG. 2 is a diagram schematically showing an xz cross section of anotherexample of the magnetic domain wall movement type magnetic recordingelement according to the first embodiment. In a magnetic domain wallmovement type magnetic recording element 100A shown in FIG. 2, adistance in the x direction between the adjacent convex portions 24 a isnot constant, and widths of the convex portions 24 a in the x directionare also different from each other. The convex portions 24 a and theconcave portions 24 b are disposed irregularly in the x direction. Whenthe convex portions 24 a and the concave portions 24 b are disposedirregularly in the x direction, the magnetic domain wall 21 is trappedirregularly, and the movement of the magnetic domain wall 21 becomesgentle. As a result, the magnetic domain wall movement type magneticrecording element 100 can easily record data in an analog manner.

Further, FIG. 3 is a diagram schematically showing a yz cross section ofanother example of the magnetic domain wall movement type magneticrecording element according to the first embodiment. In a magneticdomain wall movement type magnetic recording element 100B shown in FIG.3, a distance in the y direction between adjacent convex portions 24 ais not constant, and widths of the convex portions 24 a in the ydirection are different from each other. The convex portions 24 a andthe concave portions 24 b are disposed irregularly in the y direction.As shown in FIG. 3, the convex portions 24 a and the concave portions 24b may be disposed irregularly in the y direction, there being nolimitation to the x direction.

Also, FIG. 4 is a diagram schematically showing an xz cross section ofanother example of the magnetic domain wall movement type magneticrecording element according to the first embodiment. In a magneticdomain wall movement type magnetic recording element 100C shown in FIG.4, a height of each of the convex portions 24 a in the z direction isnot constant. As shown in FIG. 4, the height or depth of each of theconvex portions 24 a and the concave portions 24 b may be irregular inthe z direction, there being no limitation to the x direction.

The magnetic recording layer 20 can have the magnetic domain wall 21inside. The magnetic domain wall 21 is a boundary between a firstmagnetic domain 22 and a second magnetic domain 23 having magnetizationsin directions opposite to each other. When two magnetic domains areformed inside, the magnetic recording layer 20 has the magnetic domainwall 21 inside. In the magnetic domain wall movement type magneticrecording element 100 shown in FIG. 1, the first magnetic domain 22 hasa magnetization oriented in the +x direction, and the second magneticdomain 23 has a magnetization oriented in the −x direction.

The magnetic domain wall movement type magnetic recording element 100records data in a multi-valued or analog manner according to a positionof the magnetic domain wall 21 of the magnetic recording layer 20. Datarecorded on the magnetic recording layer 20 is read as a change inresistance values of the first ferromagnetic layer 10 and the magneticrecording layer 20 in the lamination direction. When the magnetic domainwall 21 moves, the ratio between the first magnetic domain 22 and thesecond magnetic domain 23 in the magnetic recording layer 20 changes.The magnetization of the first ferromagnetic layer 10 is in the samedirection as (parallel to) the magnetization of the first magneticdomain 22 and is in a direction opposite (anti-parallel) to themagnetization of the second magnetic domain 23. When the magnetic domainwall 21 moves in the x direction and an area of the first magneticdomain 22 in a portion which overlaps the first ferromagnetic layer 10when seen in the z direction increases, the resistance value of themagnetic domain wall movement type magnetic recording element 100decreases. Conversely, when the magnetic domain wall 21 moves in the −xdirection and an area of the second magnetic domain 23 in a portionwhich overlaps the first ferromagnetic layer 10 when seen in the zdirection increases, the resistance value of the magnetic domain wallmovement type magnetic recording element 100 increases.

The magnetic domain wall 21 moves by causing a current to flow in adirection in which the magnetic recording layer 20 extends or byapplying an external magnetic field. For example, when a current pulseis applied from the first electrode 41 to the second electrode 42, thefirst magnetic domain 22 spreads in a direction of the second magneticdomain 23, and the magnetic domain wall 21 moves in the direction of thesecond magnetic domain 23. That is, the position of the magnetic domainwall 21 is controlled by setting a direction and intensity of thecurrent flowing through the first electrode 41 and the second electrode42, and data is written to the magnetic domain wall movement typemagnetic recording element 100.

The magnetic recording layer 20 is configured of a magnetic body. Thesame magnetic body as that of the first ferromagnetic layer 10 can beused for the magnetic body constituting the magnetic recording layer 20.Further, the magnetic recording layer 20 preferably contains at leastone element selected from the group consisting of Co, Ni, Pt, Pd, Gd,Tb, Mn, Ge, and Ga. For example, a laminated film of Co and Ni, alaminated film of Co and Pt, a laminated film of Co and Pd, a MnGa-basedmaterial, a GdCo-based material, and a TbCo-based material can be used.Ferrimagnetic bodies such as MnGa-based materials, GdCo-based materials,and TbCo-based materials have a small saturation magnetization and canreduce a threshold current required for moving a magnetic domain wall.Furthermore, the laminated film of Co and Ni, the laminated film of Coand Pt, and the laminated film of Co and Pd have a large coercivity andcan curb a movement speed of the magnetic domain wall.

<Non-Magnetic Layer>

The non-magnetic layer 30 is sandwiched between the first ferromagneticlayer 10 and the magnetic recording layer 20. A known material can beused for the non-magnetic layer 30. For example, when the non-magneticlayer 30 is made of an insulator (when it is a tunnel barrier layer), amaterial thereof may be Al₂O₃, SiO₂, MgO, MgAl₂O₄, or the like. Inaddition, materials in which Al, Si, and Mg are partially replaced byZn, Be, or the like can be used as the non-magnetic layer 30. Amongthem, MgO and MgAl₂O₄ are materials capable of realizing coherenttunneling, and spin can be implanted efficiently. When the non-magneticlayer 30 is made of a metal, Cu, Au, Ag, or the like can be used as thematerial thereof. Furthermore, when the non-magnetic layer 30 is made ofa semiconductor, the material thereof may be Si, Ge, CuInSe₂, CuGaSe₂,Cu(ln, Ga)Se₂, or the like.

<First Electrode, Second Electrode>

The first electrode 41 and the second electrode 42 are disposed atpositions which sandwich the first ferromagnetic layer 10 in the xdirection when seen in the z direction. The first electrode 41 and thesecond electrode 42 may be made of a conductive material such as Cu, Al,and Au. Further, the first electrode 41 may be a ferromagnetic body inwhich the magnetization is oriented in the x direction, and the secondelectrode 42 may be a ferromagnetic body in which the magnetization isoriented in the −x direction. When a current passes through the firstelectrode 41 or the second electrode 42, the current is spin-polarized.When the spin-polarized current is applied to the magnetic recordinglayer 20, the ratio between the first magnetic domain 22 and the secondmagnetic domain 23 of the magnetic recording layer 20 changes.

The first electrode 41 and the second electrode 42 may be replaced withspin-orbit torque wiring. For example, spin-orbit torque wiring whichextends in the y direction is arranged at the positions of the firstelectrode 41 and the second electrode 42. When a current flows throughthe spin-orbit torque wiring, a spin Hall effect occurs in thespin-orbit torque wiring. When the spin polarized by the spin Halleffect flows into the magnetic recording layer 20, the ratio between thefirst magnetic domain 22 and the second magnetic domain 23 of themagnetic recording layer 20 changes. Both the first electrode 41 and thesecond electrode 42 may be replaced with the spin-orbit torque wiring,or only one thereof may be replaced. When both are replaced with thespin-orbit torque wiring, the direction of current flowing is reversed.

The first electrode 41 and the second electrode 42 may not be provided.In this case, the magnetic domain wall of the magnetic recording layer20 is moved by an external magnetic field.

“Control Part” <Intermediate Body (Planarization Layer)>

The intermediate body 70 is located between the base body 80 and themagnetic recording layer 20. The intermediate body 70 fills theconcave-convex structure 24 on the second surface 20B of the magneticrecording layer 20 and makes it flat. When seen from the magneticrecording layer 20, the intermediate body 70 can be regarded as aplanarization layer.

The intermediate body 70 shown in FIG. 1 is a layer having concavity andconvexity on a first surface 70A on a second surface 20B side of themagnetic recording layer 20. The first surface 70A of the intermediatebody 70 has a concave-convex structure 74 including a convex portion 74a and a concave portion 74 b. The magnetic recording layer 20 islaminated on the first surface 70A of the intermediate body 70. Theconcave-convex structure 24 of the magnetic recording layer 20B isformed by the concave-convex structure 74 on the first surface 70A ofthe intermediate body 70. The convex portion 74 a of the intermediatebody 70 corresponds to the concave portion 24 b of the magneticrecording layer 20, and the concave portion 74 b of the intermediatebody 70 corresponds to the convex portion 24 a of the magnetic recordinglayer 20.

The intermediate body 70 shown in FIG. 1 is a non-magnetic body. Theintermediate body 70 shown in FIG. 1 is an example of a trap-reinforcingmember which will be described later. When a surface of the base body 80is formed of an insulator, the intermediate body 70 may be a conductoror an insulator. When the surface of the base body 80 is a conductor,the intermediate body 70 is preferably an insulator. When theintermediate body 70 has an insulating property, a current flowingbetween the first electrode 41 and the second electrode 42 can beprevented from flowing through a portion other than the magneticrecording layer 20. When resistance of the intermediate body 70 issufficiently higher than that of the magnetic recording layer 20, aconductor, a semiconductor, or the like may be used for the intermediatebody 70.

A thickness of the intermediate body 70 is preferably 20 nm or less,more preferably 10 nm or less, and even more preferably 5 nm or less.The thickness of the intermediate body 70 is preferably 2 nm or more.Here, the thickness of the intermediate body 70 is a distance between anaverage height position of the first surface 70A and the second surface70B of the intermediate body 70. The average height position is aposition obtained by averaging the height positions of concavity andconvexity on the first surface 70A and can be confirmed by atransmission electron microscope. When the thickness of the intermediatebody 70 is within the above-described range, the concave-convexstructure 74 having a sufficient concave-convex difference on the firstsurface 70A of the intermediate body 70 can be formed.

FIG. 5 is a plan view schematically showing the magnetic domain wallmovement type magnetic recording element 100 according to the firstembodiment. In FIG. 5, the convex portions 74 a of the intermediate body70 are irregularly disposed in a xy plane. Here, the term “irregular” inthis specification means that a distance between vertices of theadjacent convex portions 74 a is not constant. The fact that thedistance between the vertices of the adjacent convex portions 74 a isnot constant is obtained as follows. First, the distances L1, L2, L3, .. . between the vertices of the convex portions 74 a located atpositions which overlaps the magnetic recording layer 20 are determined.Then, a most frequent value of the distances between the vertices of theconvex portions 74 a is obtained. When each of the distances L1, L2, L3,. . . between the vertices of the convex portions 74 a is within a rangeof ±5% of the most frequent value, the distances between the vertices ofthe adjacent convex portion 74 a are considered to be constant.Conversely, when the condition is not satisfied, it can be determinedthat the distances between the vertices of the adjacent convex portions74 a are not constant and the convex portions 74 a are irregularlydisposed in the xy plane. The magnetic recording layer 20, thenon-magnetic layer 30, and the first ferromagnetic layer 10 aresequentially laminated on the intermediate body 70. The convex portion24 a and the concave portion 24 b of the magnetic recording layer 20 areformed irregularly. FIG. 5 shows an example in which the convex portions74 a of the intermediate body 70 are irregular, but the convex portions74 a of the intermediate body 70 may be disposed regularly.

<Base Body>

The base body 80 has, for example, a substrate and an underlayerlaminated on one surface of the substrate on the intermediate body 70side. The substrate is, for example, a semiconductor substrate such assilicon. The base body 80 may have only the substrate without theunderlayer.

<Underlayer>

The underlayer is, for example, Fe, Cu, Ni, Co, Si, SiO₂, Al₂O₃, MgO, orthe like. The concavity and convexity on the first surface 70A of theintermediate body 70 are formed in relation to the underlayer. Forexample, crystal growth of the intermediate body 70 becomes granular dueto the underlayer, and the concavity and convexity are formed on thefirst surface 70A of the intermediate body 70. In addition, for example,the concavity and convexity are formed on the first surface 70A of theintermediate body 70 using the difference in surface energy between theunderlayer and the intermediate body 70.

Next, an example of a method for manufacturing the magnetic domain wallmovement type magnetic recording element 100 according to the firstembodiment will be described with reference to FIGS. 6A to 6F.

First, the base body 80 is prepared. The base 80 has a substrate 81 andan underlayer 82. Then, as shown in FIG. 6A, the intermediate body 70 isformed on one surface of the underlayer 82. The intermediate body 70 islaminated by, for example, a sputtering method, a chemical vapordeposition (CVD) method, or the like. The first surface 70A of theintermediate body 70 has concavity and convexity in relation to theunderlayer 82. For example, when a crystal of the intermediate body 70and a crystal of the underlayer 82 have different lattice constants, acrystal structure is disturbed to reduce the difference in the latticeconstant, and the concavity and convexity are formed on the firstsurface 70A. Also, for example, when there is a difference in surfaceenergy between the underlayer 82 and the intermediate body 70, theconcavity and convexity are formed on the first surface 70A. Forexample, atoms constituting the intermediate body 70 sputtered on onesurface of the underlayer 82 aggregate with each other due to thedifference in the surface energy. The atoms which are aggregatedtogether are scattered in an island shape. When film formation of theintermediate body 70 is continued, the islands are combined with eachother, and the intermediate body 70 having the concavity and convexityon the first surface 70A is formed. The positions in the x direction andthe positions in the y direction of the convex portions of the concavityand convexity formed on the first surface 70A may be regular orirregular, and the heights of the convex portions in the z direction maybe constant or different.

Next, as shown in FIG. 6B, a magnetic body 28 is laminated on onesurface of the intermediate body 70. A first surface 28A of the magneticbody 28 has concavity and convexity which reflect a shape of the firstsurface 70A of the intermediate body 70.

Further, as shown in FIG. 6C, anisotropic sputtering may be performedwhen the magnetic body 28 is laminated. The anisotropic sputtering is amethod in which ions are sputtered to a film-forming object (theintermediate body 70) in an oblique direction.

When ions are supplied in an oblique direction, a film forming speedchanges in a plane of the film-forming body (the intermediate body 70),and the first surface 28A of the magnetic body 28 is planarized withrespect to the first surface 70A of the intermediate body 70.

Next, as shown in FIG. 6D, the first surface 28A of the magnetic body 28is planarized. The planarization is performed by, for example, chemicalmechanical polishing, dry etching, wet etching, or the like. As shown inFIG. 6C, when the anisotropic sputtering is performed, a process inwhich the first surface 28A is planarized may not be performed.

Next, as shown in FIG. 6E, a magnetic body 29 is laminated on the firstsurface 28A of the magnetic body 28. The magnetic body 28 and themagnetic body 29 are the same. The magnetic body 28 and the magneticbody 29 are combined to form the magnetic recording layer 20.

Next, as shown in FIG. 6F, the non-magnetic layer 30 and the firstferromagnetic layer 10 are sequentially laminated on one surface of themagnetic recording layer 20. Then, unnecessary portions of thenon-magnetic layer 30 and the first ferromagnetic layer 10 are removedby photolithography or the like. With such a procedure, the magneticdomain wall movement type magnetic recording element 100 according tothe first embodiment can be manufactured.

As described above, since the magnetic domain wall movement typemagnetic recording element 100 according to the first embodiment has theconcave-convex structure 24 on a surface of the magnetic recording layer20 on the back surface side (the side opposite to the firstferromagnetic layer 10), and the concave-convex structure 24 serves as atrap site for the magnetic domain wall 21, controllability of themovement of the magnetic domain wall 21 can be improved. Further, thesecond surface 20B on which the concave-convex structure 24 is formedcorresponds to a back surface of the first surface 20A on which thefirst ferromagnetic layer 10 is laminated, and has little effect on theMR ratio of the magnetic domain wall movement type magnetic recordingelement 100. That is, noise of the magnetic domain wall movement typemagnetic recording element 100 can be curbed.

Further, when a trap site is separately provided around the magneticrecording layer 20, it is necessary to maintain a predetermined distancebetween the magnetic recording layer 20 and the trap site due to aprocess restriction. On the other hand, in the embodiment, the backsurface of the magnetic recording layer 20 is the trap site, themagnetic domain wall 21 can be trapped at a closer position than a casein which the trap site is provided around the magnetic recording layer20, and thus the controllability of the movement of the magnetic domainwall 21 can be further improved. Further, when the trap site is providedon a side surface of the magnetic recording layer 20, the concavity andconvexity in which a difference between the concavity and convexity isabout a few tens of nm are formed on the side surface due to a problemof processing accuracy of photolithography or the like. In other words,an extra space of about a few tens of nm is required outside the firstferromagnetic layer 10. On the other hand, the magnetic domain wallmovement type magnetic recording element 100 according to the embodimenthas the trap site in the z direction and does not require an extra spacein the xy directions.

Further, since the magnetic domain wall movement type magnetic recordingelement 100 according to the embodiment does not have the concave-convexstructure 24 on the surface side (the first ferromagnetic layer 10side), a problem that noise is generated when a density of a currentflowing on the surface side becomes discontinuous in the concave-convexstructure can be avoided.

Further, the magnetic domain wall movement type magnetic recordingelement 100 according to the embodiment does not require physicalprocessing of the first ferromagnetic layer in the manufacturing processand can also avoid a problem that noise is generated at the time ofoperation due to an effect of processing damage.

Although an example of the first embodiment has been described indetail, the first embodiment is not limited to this example, and variousmodifications and changes may be made within the scope of the presentinvention described in the appended claims.

FIG. 7 is a cross-sectional view schematically showing Modified Example1 of the magnetic domain wall movement type magnetic recording elementaccording to the first embodiment. A magnetic domain wall movement typemagnetic recording element 100D according to Modified Example 1 isdifferent from the magnetic domain wall movement type magnetic recordingelement 100 shown in FIG. 1 in that the intermediate body 70 has nolayer formed and is scattered on one surface of the base body 80. Alsoin this case, the second surface 20B of the magnetic recording layer 20has the concave-convex structure 24, and the same effect as in themagnetic domain wall movement type magnetic recording element 100 can beobtained.

The magnetic domain wall movement type magnetic recording element 100Daccording to Modified Example 1 is manufactured by stopping the filmformation of the intermediate body 70 before the islands are combinedwhen the intermediate body 70 is laminated.

Second Embodiment

FIG. 8 is a schematic cross-sectional view of a magnetic domain wallmovement type magnetic recording element according to a secondembodiment. The magnetic domain wall movement type magnetic recordingelement 101 shown in FIG. 8 is different from the magnetic domain wallmovement type magnetic recording element 100 shown in FIG. 1 in that theintermediate body 70 includes a trap-reinforcing member 90 and aninsulating layer 91 which covers the trap-reinforcing member 90 from aposition near the base body 80. The same parts as those of the magneticdomain wall movement type magnetic recording element 100 are designatedby the same reference numerals, and description thereof will be omitted.

In FIG. 8, the trap-reinforcing member 90 is scattered on one surface ofthe base body 80. The trap-reinforcing member 90 may be made of anon-magnetic material such as Ta, Al, or Cu, or may be made of amagnetic material such as Ni, Fe, or Co. When the trap-reinforcingmember 90 is made of a non-magnetic material, the difference in magneticpotential energy can be clarified between the convex portion 24 a andthe concave portion 24 b in the concave-convex structure 24 of themagnetic recording layer, and a magnetic domain wall trapping functioncan be enhanced. Further, when the trap-reinforcing member 90 is made ofa magnetic material, the magnetic domain wall 21 can be trapped morestrongly by magnetically coupling with the magnetization of the magneticrecording layer 20, as compared with the case in which thetrap-reinforcing member 90 is made of a non-magnetic material.

When a film is formed by sputtering a material to form the insulatinglayer 91 after \the trap-reinforcing member 90 is formed, according tofilm forming conditions, the ratio of the thickness of a planarizationmaterial to be formed can be adjusted at an upper surface and a sidesurface of the trap-reinforcing member 90. At this time, the ratiobetween the width of the trap-reinforcing member 90 and the thickness ofthe planarization material is 1:1 to 2:1. Therefore, in an extendingdirection (the x direction) of the magnetic recording element 20, thewidth of the trap-reinforcing member 90 is about 0.3 to 0.5 times thewidth of the concave portion 24 b.

The insulating layer 91 covers the surface of the trap-reinforcingmember 90 scattered in an island shape. The insulating layer 91 isformed by reflecting surface shapes of the base body 80 and thetrap-reinforcing member 90. Therefore, the concave-convex structure 74including the convex portion 74 a and the concave portion 74 b is formedon the first surface 70A of the intermediate body 70. Since the magneticrecording layer 20 is formed on the first surface 70A of theintermediate body 70, the second surface 20B has the concave-convexstructure 24.

In the insulating layer 91, at least a portion between an inner wall ofthe concave portion 24 b and the trap-reinforcing member 90 hasinsulating properties. The insulating layer 91 preferably has insulatingproperties as a whole. The insulating layer 91 electrically separatesthe magnetic recording layer 90 from the base body 80. The base body 80is formed on the side of the intermediate body 70 opposite to themagnetic recording layer 20. The base body 80 is in contact with one endof the trap-reinforcing member 90.

When a surface energy of a material constituting the surface of the basebody 80 is γ_(A), and a surface energy of a material of thetrap-reinforcing member 90 is γ_(B), γ_(B)<γ_(A), and a surface energymismatch Γ_(AB) defined by the following Equation (1) is preferablylarger than 0.5. Here, the material constituting the surface of the basebody 80 is a material which constitutes the underlayer when the basebody 80 is formed of the substrate and the base layer, and the materialis a material which constitutes the substrate when the base body 80 isformed of the substrate. In the first embodiment, the materialconstituting the intermediate body 70 and the material constituting thesurface of the base body 80 also preferably satisfy the samerelationship.

$\begin{matrix}{\left\lbrack {{Math}\mspace{14mu} 2} \right\rbrack \mspace{661mu}} & \; \\{\Gamma_{AB} = {2{\frac{\gamma_{A} - \gamma_{B}}{\gamma_{A} + \gamma_{B}}}}} & (2)\end{matrix}$

When the surface energy of the surface of the base body 80 and thesurface energy of the trap-reinforcing member 90 satisfy the aboverelationship, the trap-reinforcing member 90 grows in an island shapeonly by performing a film forming process. In this case, sincepatterning for forming the trap-reinforcing member 90 is not required,the manufacturing process can be simplified.

Table 1 shows an example of a combination of materials of the surface ofthe base body 80 and the trap-reinforcing member 90 which satisfies theabove relationship.

TABLE 1 Base body Trap-reinforcing member Material γ_(A)(mNm⁻¹) Materialγ_(B)(mNm⁻¹) Γ_(AB) Al 1085 SiO₂ 290 1.16 1085 Al₂O₃ 580 0.61 1085 MgO520 0.70 Si 1107 SiO₂ 290 1.17 1107 Al₂O₃ 580 0.62 1107 MgO 520 0.72 Au1616 SiO₂ 290 1.39 1616 Al₂O₃ 580 0.94 1616 MgO 520 1.03 1616 Al 10850.39 Cu 1934 SiO₂ 290 1.48 1934 Al₂O₃ 580 1.08 1934 MgO 520 1.15 1934 Al1085 0.56 Pd 2043 SiO₂ 290 1.50 2043 Al₂O₃ 580 1.12 2043 MgO 520 1.192043 Al 1085 0.61 Cr 2056 SiO₂ 290 1.51 2056 Al₂O₃ 580 1.12 2056 MgO 5201.19 2056 Al 1085 0.62 Ti 2570 SiO₂ 290 1.59 2570 Al₂O₃ 580 1.26 2570MgO 520 1.33 2570 Al 1085 0.81 Pt 2691 SiO₂ 290 1.61 2691 Al₂O₃ 580 1.292691 MgO 520 1.35 2691 Al 1085 0.85 Ta 3018 SiO₂ 290 1.65 3018 Al₂O₃ 5801.36 3018 MgO 520 1.41 3018 Al 1085 0.94 Ru 3409 SiO₂ 290 1.69 3409Al₂O₃ 580 1.42 3409 MgO 520 1.47 3409 Al 1085 1.03 Al₂O₃ 580 SiO₂ 2900.67 MgO 520 SiO₂ 290 0.57

Next, an example of a method for manufacturing the magnetic domain wallmovement type magnetic recording element 101 according to the secondembodiment will be described with reference to FIGS. 9A to 9F.

First, the base 80 is prepared. The base 80 includes the substrate 81and the underlayer 82. Next, as shown in FIG. 9A, the trap-reinforcingmember 90 is formed on one surface of the underlayer 82. Thetrap-reinforcing member 90 is laminated by, for example, a sputteringmethod, a chemical vapor deposition (CVD) method, or the like. Thetrap-reinforcing member 90 grows in an island shape. When a film isformed under a condition that the thickness of the trap-reinforcingmember 90 is equal to or less than the thickness at which thetrap-reinforcing member 90 becomes a layer, the trap-reinforcing member90 grows into a nucleus and has an island shape. The condition that thethickness of the trap-reinforcing member 90 is equal to or less than thethickness at which the trap-reinforcing member 90 becomes a layer is acondition that is equal to or less than a condition that thetrap-reinforcing member 90 theoretically has a thickness correspondingto several atomic layers. Even under the condition of a film having athickness corresponding to several atomic layers being formedtheoretically, the islands which are grown into a nucleus are notactually combined, and thus the trap-reinforcing member 90 is scatteredin an island shape. Also, for example, when the trap-reinforcing member90 is selected in consideration of the difference in the surface energywith respect to the underlayer 82, the trap-reinforcing member 90 isformed in an island shape.

Next, as shown in FIG. 9B, the insulating layer 91 is laminated on onesurface of the trap-reinforcing member 90. The insulating layer 91covers the surfaces of the base body 80 and the trap-reinforcing member90. As a result, the first surface 70A of the intermediate body 70 hasthe concavity and convexity.

Next, as shown in FIG. 9C, the magnetic body 28 is laminated on onesurface of the intermediate body 70. The first surface 28A of themagnetic body 28 has the concavity and convexity which reflect the shapeof the first surface 70A of the intermediate body 70.

Further, as shown in FIG. 9D, the anisotropic sputtering may beperformed when the magnetic body 28 is laminated. The first surface 28Aof the magnetic body 28 is planarized with respect to the first surface70A of the intermediate body 70.

Next, as shown in FIG. 9E, the first surface 28A of the magnetic body 28is planarized. The planarization is performed by, for example, chemicalmechanical polishing, dry etching, wet etching, or the like. As shown inFIG. 9D, when the first surface 28A is planarized by another method, theplanarizing process may not be performed.

Next, as shown in FIG. 9F, the magnetic body 29 is laminated on thefirst surface 28A of the magnetic body 28. The magnetic body 28 and themagnetic body 29 are the same. The magnetic body 28 and the magneticbody 29 are combined to form the magnetic recording layer 20.

Next, as shown in FIG. 9E, the non-magnetic layer 30 and the firstferromagnetic layer 10 are sequentially laminated on one surface of themagnetic recording layer 20. Then, the unnecessary portions of thenon-magnetic layer 30 and the first ferromagnetic layer 10 are removedby photolithography or the like. With such a procedure, the magneticdomain wall movement type magnetic recording element 101 according tothe second embodiment can be manufactured.

In the magnetic domain wall movement type magnetic recording element 101according to the embodiment, the trap-reinforcing member 90 is coveredwith the insulating layer 91. The insulating layer 91 electricallyseparates the magnetic recording layer 20 from the base body 80.Therefore, the degree of freedom in selecting the trap-reinforcingmember 90 is increased. Thus, the controllability of the movement of themagnetic domain wall 21 can be further enhanced as compared with themagnetic domain wall movement type magnetic recording element 100 of thefirst embodiment.

Although an example of the second embodiment has been described indetail, the second embodiment is not limited to this example, andvarious modifications and changes may be made within the scope of thepresent invention described in the appended claims. For example, thesecond embodiment can employ the same modified example as the firstembodiment.

FIG. 10 is a cross-sectional view schematically showing Modified Example2 of the magnetic domain wall movement type magnetic recording elementaccording to the second embodiment. A magnetic domain wall movement typemagnetic recording element 101A according to Modified Example 2 isdifferent from the magnetic domain wall movement type magnetic recordingelement 100 shown in FIG. 1 in that the adjacent trap-reinforcingmembers 90 are combined with each other and a layer is formed. Thetrap-reinforcing member 90 is a layer having concavity and convexity.The insulating layer 91 reflects the surface shape of thetrap-reinforcing member 90. Therefore, the first surface 70A of theintermediate body 70 has the concave-convex structure 74. Also in thiscase, the second surface 20B of the magnetic recording layer 20 has theconcave-convex structure 24, and the same effect as in the magneticdomain wall movement type magnetic recording element 101 can beobtained.

The magnetic domain wall movement type magnetic recording element 101Aaccording to Modified Example 2 is manufactured by continuing the filmformation until islands are combined with each other when thetrap-reinforcing member 90 is laminated.

Third Embodiment

FIGS. 11 and 12 are schematic cross-sectional views of magnetic domainwall movement type magnetic recording elements according to a thirdembodiment. The magnetic domain wall movement type magnetic recordingelements 102 and 103 shown in FIGS. 11 and 12 are different from themagnetic domain wall movement type magnetic recording element 101 shownin FIG. 1 in that, in the concave-convex structure 24 of the magneticrecording layer, some of the concave portions or the convex portions(the convex portions or the concave portions having a second shape) havedifferent shapes from other concave portions or convex portions (theconvex portions or the concave portions having a first shape). When thefirst shape is a convex portion, the second shape is a convex portion,and when the first shape is a concave portion, the second shape is aconcave portion. The same parts as those of the magnetic domain wallmovement type magnetic recording element according to the firstembodiment are designated by the same reference numerals, anddescription thereof will be omitted. Hereinafter, a case in which thefirst shape is the convex portion 25 and the second shape is the convexportion 24 a will be described as an example.

In the magnetic domain wall movement type magnetic recording element 102shown in FIG. 11, the convex portion 25 having the second shape(hereinafter, referred to as a first convex portion 25) in theconcave-convex structure 24 of the magnetic recording layer 20 is largerthan the convex portion 24 a having the first shape in the xz crosssection in the extending direction (the x direction, a first direction)of the magnetic recording layer. Therefore, since the first convexportion 25 has a larger volume than the other convex portions 24 a, theintensity of a generated magnetic field is large, and the movement ofthe magnetic domain wall 21 can be more strongly restricted than by theother convex portion 24 a. In plan view from the z direction, at least apart of the first convex portion 25 is located inward from the firstferromagnetic layer 10 and overlaps an end surface of the firstferromagnetic layer 10. When the end surface of the first ferromagneticlayer 10 is inclined, the end surface may overlap any part of the endsurface. In plan view, when the entire first convex portion 25 islocated inward from the first ferromagnetic layer 10 and overlaps theend surface of the first ferromagnetic layer 10, the movement range ofthe magnetic domain wall 21 is controlled to be within a range whichoverlaps the first ferromagnetic layer 10. The resistance value of themagnetic domain wall movement type magnetic recording element 102changes due to the difference in the magnetization state between thefirst ferromagnetic layer 10 and the magnetic recording layer 20. Evenwhen the magnetic domain wall 21 moves to a position at which it doesnot overlap the first ferromagnetic layer 10, a change in the resistancevalue does not occur. That is, it is possible to suppress the magneticdomain wall 21 from reaching a portion that does not affect the changein the resistance value by controlling the movement range of themagnetic domain wall 21. Further, the range of the change in theresistance value of the magnetic domain wall movement type magneticrecording element 102 can be specified by defining the movement range ofthe magnetic domain wall 21.

In the magnetic domain wall movement type magnetic recording element 103shown in FIG. 12, a convex portion 26 having the second shape(hereinafter, referred to as a second convex portion 26) in theconcave-convex structure 24 of the magnetic recording layer 20 is largerthan the convex portion 24 a having the first shape in the xz crosssection in the thickness direction (the z direction) of the magneticrecording layer. Therefore, since the second convex portion 26 has alarger volume than the other convex portion 24 a, the intensity of agenerated magnetic field is large, and the movement of the magneticdomain wall 21 can be more strongly restricted than by the other convexportion 24 a. In plan view from the z direction, at least a part of thesecond convex portion 26 is located inward from the first ferromagneticlayer 10 and overlaps an end surface of the first ferromagnetic layer10. Thus, the movement range of the magnetic domain wall 21 can becontrolled, and it is possible to suppress the magnetic domain wall 21from reaching a portion that does not affect the change in theresistance value. Further, the range of the change in the resistancevalue of the magnetic domain wall movement type magnetic recordingelement 103 can be specified by defining the movement range of themagnetic domain wall 21.

Here, although the volumes of the convex portions 25 and 26 having thesecond shape and the convex portion 24 a having the first shape arecompared, the comparison may be made based on areas of the convexportions 25 and 26 having the second shape and the convex portion 24 ahaving the first shape in the xz cross section. The difference in theintensity of the magnetic field in the x direction controls the movementof the magnetic domain wall 21 in the x direction. Therefore, even whenthe volume is constant, the movement range of the magnetic domain wall21 can be restricted when there is a difference between the convexportions 25 and 26 having the second shape and the convex portion 24 ahaving the first shape in the xz cross section.

In the magnetic domain wall movement type magnetic recording elements102 and 103 according to the third embodiment, the trapping function canbe locally strengthened at positions of the convex portions larger thanother convex portions, such as the first convex portion 25 and thesecond convex portion 26, and thus the movement speed of the magneticdomain wall 21 in the vicinity thereof can be largely changed.Therefore, when electric resistance and the like are continuouslymeasured while the magnetic domain wall 21 is moved, a change pointoccurs in measurement data, and a position of the magnetic domain wall21 below the first ferromagnetic layer 10 can be detected from thischange point.

The change in the resistance value of the magnetic domain wall movementmagnetic recording elements 102 and 103 occurs when the magnetic domainwall 21 is present at a position at which it overlaps the firstferromagnetic layer 10 in plan view. The concave portion or the convexportion of the second shape having a strong trapping function ispreferably located at a position at which it overlaps the firstferromagnetic layer 10 in plan view in the lamination direction L of therecording part 60. Further, the concave or convex portion having thesecond shape is preferably disposed inward from an end portion of thefirst ferromagnetic layer 10 in the x direction and more preferablyoverlaps the end portion of the first ferromagnetic layer 10. When thereis the concave or convex portion of the second shape having the strongtrapping function at a position at which it overlaps both ends of thefirst ferromagnetic layer 10 in the x direction, an upper limit and alower limit of the change in the resistance value are easily determined.That is, a start point and an end point of the multi-valued recordingcan be clarified, and reliability of data of the magnetic domain wallmovement type magnetic recording elements 102 and 103 can be improved.

Although changing of the shape of the convex portion in the crosssections of the magnetic domain wall movement type magnetic recordingelements 102 and 103 has been described, for example, the shape of theconvex portion may be changed in plan view shape in the laminationdirection L. Further, as a method other than changing the shape, forexample, even when the trap-reinforcing member 90 shown in the secondembodiment is provided only in some of the concave portions, the sameeffect as when the shape of the convex portion is changed can beobtained. Furthermore, even when the trap-reinforcing members 90 areprovided in all the concave portions and only the trap-reinforcingmembers 90 provided in some of the concave portions are made of amaterial having a relatively strong trapping function, the same effectcan be obtained.

Fourth Embodiment

FIG. 13 is a schematic cross-sectional view of a magnetic domain wallmovement type magnetic recording element according to a fourthembodiment. The magnetic domain wall movement type magnetic recordingelement 104 shown in FIG. 13 is different from the magnetic domain wallmovement type magnetic recording element 100 shown in FIG. 1 in that asecond ferromagnetic layer 50 which reflects the magnetization state ofthe magnetic recording layer 20 is provided between the magneticrecording layer 20 and the non-magnetic layer 30. The same parts asthose of the magnetic domain wall movement type magnetic recordingelement 100 according to the first embodiment are designated by the samereference numerals, and description thereof will be omitted. Theconstitution of the magnetic domain wall movement type magneticrecording element according to the fourth embodiment can be applied toany of the elements according to the first to third embodiments.

The second ferromagnetic layer 50 includes a magnetic body. The samemagnetic body as that of the first ferromagnetic layer 10 can be usedfor a magnetic body constituting the second ferromagnetic layer 50.

The second ferromagnetic layer 50 is adjacent to the magnetic recordinglayer 20. The magnetization of the second ferromagnetic layer 50 ismagnetically coupled to the magnetization of the magnetic recordinglayer 20. Therefore, the second ferromagnetic layer 50 reflects amagnetic state of the magnetic recording layer 20. When the secondferromagnetic layer 50 and the magnetic recording layer 20 areferromagnetically coupled, the magnetic state of the secondferromagnetic layer 50 becomes the same as the magnetization state ofthe magnetic recording layer 20, and when the second ferromagnetic layer50 and the magnetic recording layer 20 are antiferromagneticallycoupled, the magnetic state of the second ferromagnetic layer 50 isopposite to the magnetization state of the magnetic recording layer 20.

When the second ferromagnetic layer 50 is inserted between the magneticrecording layer 20 and the non-magnetic layer 30, functions of thesecond ferromagnetic layer 50 and the magnetic recording layer 20 in themagnetic domain wall movement type magnetic recording element 104 can beseparated. The MR ratio of the magnetic domain wall movement typemagnetic recording element 104 is caused by a change in themagnetization state of two magnetic bodies (the first ferromagneticlayer 10 and the second ferromagnetic layer 50) which sandwich thenon-magnetic layer 30. Therefore, the second ferromagnetic layer 50 canmainly have a function of improving the MR ratio, and the magneticrecording layer 20 can mainly have a function of moving the magneticdomain wall 21.

When the functions of the second ferromagnetic layer 50 and the magneticrecording layer 20 are separated, the degree of freedom of the magneticbody constituting each increases. The second ferromagnetic layer 50 canbe made of a material which provides a coherent tunnel effect with thefirst ferromagnetic layer 10, and the magnetic recording layer 20 can bemade of a material which reduces the movement speed of the magneticdomain wall.

As described above, also in the magnetic domain wall movement typemagnetic recording element 104 according to the fourth embodiment, thesame effect as that in the first embodiment can be obtained. Further,the degree of freedom in selecting materials used for the layers can beincreased by inserting the second ferromagnetic layer 50. In addition,the MR ratio of the magnetic domain wall movement type magneticrecording element 104 can be further increased by increasing the degreeof freedom in selecting materials.

Fifth Embodiment

FIG. 14 is a schematic plan view of a magnetic domain wall movement typemagnetic recording element 105 according to a fifth embodiment in which“a configuration having a plurality of recording parts 60” is added tothe second embodiment. The magnetic domain wall movement type magneticrecording element 105 shown in FIG. 14 is different from the magneticdomain wall movement type magnetic recording element 101 shown in FIG. 8in that a plurality of recording parts 60 are provided. The same partsas those of the magnetic domain wall movement type magnetic recordingelement 101 according to the second embodiment are designated by thesame reference numerals, and description thereof will be omitted. Theconfiguration of the magnetic domain wall movement type magneticrecording element 105 according to the fifth embodiment can be appliedto any of the elements of the other embodiments.

The magnetic domain wall movement type magnetic recording element 105shown in FIG. 14 has a plurality of recording parts 60 which extendsubstantially parallel to each other in the x direction (the firstdirection). The plurality of recording parts 60 are arranged atpredetermined intervals in a second direction (the y direction in FIG.14) which intersects the x direction. The plurality of recording parts60 are formed on the control unit 75 which spreads in the xy plane.Further, the trap-reinforcing member 90 extends over the plurality ofrecording parts 60. For example, the trap-reinforcing member 90 extendsto be in communication with the inside of the concave portion 24 bconstituting each of the recording parts and to cross the magneticrecording layer 20 in a direction intersecting the x direction.

The respective recording parts 60 are preferably disposed so that theconcave-convex structures 24 (the positions of the convex portions 24 aand the concave portions 24 b) of the respective magnetic recordinglayers 20 overlap each other in plan view in the y direction. Thetrap-reinforcing member 90 can be formed linearly in the y direction.Further, in this case, a distance between the trap sites of the adjacentmagnetic recording layers (between the convex portions 24 a) can be madeuniform, and an amount of movement of the magnetic domain wall withrespect to a pulse input can be made uniform. That is, it becomes easyto simultaneously control the movement of the magnetic domain wall 21 ineach of the plurality of recording parts 60.

Since the trap-reinforcing member 90 is present over the plurality ofrecording parts 60, the multi-valued recording can be performed in eachof the recording parts 60 in the same manner That is, a multi-valuedsignal generated for each of the recording parts 60 can be changedevenly. The difference in signal strength between the recording parts 60is reduced by making a threshold for recording data in each of therecording parts 60 constant. As a result, noise of the magnetic domainwall movement type magnetic recording element 105 as a whole is reduced,and multi-valued recording of data can be stably performed.

As described above, although the magnetic domain wall movement typemagnetic recording element according to the embodiment has beendescribed in detail with reference to the drawings, each of theconstitutions and the combination thereof in each of the embodiments isan example, and addition, omission, substitution, and other changes ofthe constitution are possible without departing from the gist of thepresent invention.

FIG. 15 is a cross-sectional view schematically showing Modified Example3 of the magnetic domain wall movement type magnetic recording elementaccording to the fifth embodiment. A magnetic domain wall movement typemagnetic recording element 105A according to Modified Example 3 isdifferent from the magnetic domain wall movement type magnetic recordingelement 105 in that the trap-reinforcing members 90 are not linear butare scattered in the xy plane.

The trap-reinforcing member 90 is scattered irregularly in the xy plane.The plurality of recording parts 60 are formed on the trap-reinforcingmember 90 which spreads in the xy plane. The trap-reinforcing member 90spreads over the plurality of recording parts 60 in the xy plane.

The movement of the magnetic domain wall 21 in each of the recordingparts 60 is controlled by the trap-reinforcing member 90 which spreadsin the xy plane. When the trap-reinforcing member 90 is scatteredirregularly, the movement of the magnetic domain wall 21 becomesirregular. Further, the magnetic domain wall 21 is inclined in the ydirection. Since a data change in each of the recording parts 60 becomesirregular, the magnetic domain wall movement type magnetic recordingelement 105A is excellent in analog recording of data. Further, when thetrap-reinforcing member 90 forms a layer, the “trap-reinforcing member90” can be replaced with the “convex portion of the trap-reinforcingmember 90”.

Sixth Embodiment

FIG. 16 is a plan view of a magnetic recording array 200 according to asixth embodiment. In the magnetic recording array 200 shown in FIG. 16,the recording parts 60 of the magnetic domain wall movement typemagnetic recording element have a 3×3 matrix arrangement. FIG. 16 is anexample of a magnetic recording array, and the type, number, andarrangement of the recording parts 60 are arbitrary. Further, thecontrol part may be provided to be present over all the recording parts60, or may be provided for each of the recording parts 60.

The magnetic domain wall movement type magnetic recording element 100 isconnected to one word line WL1 to WL3, one bit line BL1 to 3, and oneread line RL1 to RL3.

A pulse current is applied to the magnetic recording layer 20 of anarbitrary recording part 60 by selecting the word lines WL1 to WL3 andthe bit lines BL1 to BL3 to which a current is applied, and a writeoperation is performed. In addition, a current flows in the laminationdirection of the arbitrary recording part 60 by selecting the read linesRL1 to RL3 and the bit lines BL1 to BL3 to which a current is applied,and a reading operation is performed. The word lines WL1 to WL3, the bitlines BL1 to BL3, and the read lines RL1 to RL3 to which a current isapplied can be selected by a transistor or the like. Since each of therecording parts 60 records information in multiple values, ahigh-capacity magnetic recording array can be realized.

Although the embodiments have been described in detail, the presentinvention is not limited to a specific embodiment, and variousmodifications and changes may be made within the scope of the presentinvention described in the appended claims

REFERENCE SIGNS LIST

10 First ferromagnetic layer

20 Magnetic recording layer

20A, 70A, 28A First surface

20B, 70B Second surface

21 Magnetic domain wall

22 First magnetic domain

23 Second magnetic domain

24, 74 Concave-convex structure

24 a, 74 a Convex portion

24 b, 74 b Concave portion

25 First convex portion

26 Second convex portion

28, 29 Magnetic body

30 Non-magnetic layer

41 First electrode

42 Second electrode

50 Second ferromagnetic layer

60 Recording part

70 Intermediate body (planarization layer)

75 Control part

80 Base body

81 Substrate

82 Underlayer

90 Trap-reinforcing member

91 Insulating layer

100 to 105, 100A, 101A, 105A Magnetic domain wall movement type magneticrecording element

200 Magnetic recording array

1. A magnetic domain wall movement type magnetic recording element,comprising: a first ferromagnetic layer which includes a ferromagneticbody; a non-magnetic layer which faces the first ferromagnetic layer;and a magnetic recording layer which faces a surface of the non-magneticlayer on a side opposite to the first ferromagnetic layer and extends ina first direction, wherein the magnetic recording layer has aconcave-convex structure on a second surface opposite to a first surfacewhich faces the non-magnetic layer.
 2. The magnetic domain wall movementtype magnetic recording element according to claim 1, wherein the firstsurface has a smaller arithmetic average roughness than an arithmeticaverage roughness of the second surface.
 3. The magnetic domain wallmovement type magnetic recording element according to claim 1, wherein,in the concave-convex structure, vertex positions of convex portionsconstituting the concave-convex structure are irregularly spaced in planview in a lamination direction.
 4. The magnetic domain wall movementtype magnetic recording element according to claim 1, furthercomprising: a base body which faces the second surface of the magneticrecording layer; and an intermediate body which is located between thebase body and the magnetic recording layer.
 5. The magnetic domain wallmovement type magnetic recording element according to claim 4, wherein:the intermediate body is a non-magnetic trap-reinforcing member, and thetrap-reinforcing member is layers which are scattered on one surface ofthe base body or a layer which has concavity and convexity on the secondsurface side of the magnetic recording layer.
 6. The magnetic domainwall movement type magnetic recording element according to claim 4,wherein: the intermediate body has a trap-reinforcing member, and aninsulating layer which covers the trap-reinforcing member from aposition near the base body, and the trap-reinforcing member is layerswhich are scattered on one surface of the base body or a layer which hasconcavity and convexity on the second surface side of the magneticrecording layer.
 7. The magnetic domain wall movement type magneticrecording element according to claim 5 wherein: one end of thetrap-reinforcing member is in contact with the base body, and when asurface energy of a material constituting a surface of the base body isγ_(A), and a surface energy of a material of the trap-reinforcing memberis γ_(B), γ_(B)<γ_(A), and a surface energy mismatch Γ_(AB) defined bythe following Equation (1) is larger than 0.5 $\begin{matrix}{\left\lbrack {{Math}\mspace{14mu} 1} \right\rbrack \mspace{661mu}} & \; \\{\Gamma_{AB} = {2{{\frac{\gamma_{A} - \gamma_{B}}{\gamma_{A} + \gamma_{B}}}.}}} & (1)\end{matrix}$
 8. The magnetic domain wall movement type magneticrecording element according to claim 5 wherein: a plurality of recordingparts which includes the first ferromagnetic layer, the nonmagneticlayer and the magnetic recording layer are provided, the plurality ofrecording parts are arranged in a second direction which intersects thefirst direction, and the trap-reinforcing member spreads in a same planeover the plurality of recording parts.
 9. The magnetic domain wallmovement type magnetic recording element according to claim 5, wherein:a plurality of recording parts which includes the first ferromagneticlayer, the nonmagnetic layer and the magnetic recording layer areprovided, and the trap-reinforcing member or a convex portion of thetrap-reinforcing member extends in a second direction which intersectsthe first direction over the plurality of recording parts.
 10. Themagnetic domain wall movement type magnetic recording element accordingto claim 1, wherein the concave-convex structure has periodicity in thefirst direction.
 11. The magnetic domain wall movement type magneticrecording element according to claim 1, wherein the concave-convexstructure has a concave portion or a convex portion having a firstshape, and a concave portion or a convex portion having a second shapehaving a larger volume than that of the first shape.
 12. The magneticdomain wall movement type magnetic recording element according to claim11, wherein the concave portion or the convex portion having the secondshape is located at a position at which the concave portion or theconvex portion having the second shape overlaps an end surface of thefirst ferromagnetic layer in plan view in the lamination direction. 13.The magnetic domain wall movement type magnetic recording elementaccording to claim 11, wherein the concave or convex portion having thesecond shape is larger than the concave or convex portion having thefirst shape in the first direction.
 14. The magnetic domain wallmovement type magnetic recording element according to claim 11, whereinthe concave or convex portion having the second shape is larger than theconcave or convex portion having the first shape in the laminationdirection.
 15. The magnetic domain wall movement type magnetic recordingelement according to claim 1, wherein a second ferromagnetic layer whichreflects a magnetization state of the magnetic recording layer isprovided between the magnetic recording layer and the non-magneticlayer.
 16. A magnetic domain wall movement type magnetic recordingelement comprising: a recording part which includes: a firstferromagnetic layer which includes a ferromagnetic body; a magneticrecording layer which is laminated on one side of the firstferromagnetic layer, extends in a first direction which intersects alamination direction, has a magnetic domain wall, and has aconcave-convex structure which traps the magnetic domain wall on a sideopposite to the first ferromagnetic layer; and a non-magnetic layersandwiched between the first ferromagnetic layer and the magneticrecording layer; and a control part which has a planarization layerlaminated on a side of the magnetic recording layer opposite to thefirst ferromagnetic layer and planarizes the concave-convex structure ofthe magnetic recording layer.
 17. The magnetic domain wall movement typemagnetic recording element according to claim 2, wherein, in theconcave-convex structure, vertex positions of convex portionsconstituting the concave-convex structure are irregularly spaced in planview in a lamination direction.
 18. The magnetic domain wall movementtype magnetic recording element according to claim 2, furthercomprising: a base body which faces the second surface of the magneticrecording layer; and an intermediate body which is located between thebase body and the magnetic recording layer.
 19. The magnetic domain wallmovement type magnetic recording element according to claim 3, furthercomprising: a base body which faces the second surface of the magneticrecording layer; and an intermediate body which is located between thebase body and the magnetic recording layer.
 20. The magnetic domain wallmovement type magnetic recording element according to claim 6, wherein:one end of the trap-reinforcing member is in contact with the base body,and when a surface energy of a material constituting a surface of thebase body is γ_(A), and a surface energy of a material of thetrap-reinforcing member is γ_(B), γ_(B)<γ_(A), and a surface energymismatch Γ_(AB) defined by the following Equation (1) is larger than 0.5$\begin{matrix}{\left\lbrack {{Math}\mspace{14mu} 1} \right\rbrack \mspace{661mu}} & \; \\{\Gamma_{AB} = {2{{\frac{\gamma_{A} - \gamma_{B}}{\gamma_{A} + \gamma_{B}}}.}}} & (1)\end{matrix}$